1. Field of the Invention
The present invention relates to a method of manufacturing a toner, a toner obtained by a method thereof, a one-component developer, a two-component developer, a developing device, and an image forming apparatus.
2. Description of the Related Art
An image forming apparatus employing an electrophotography forms an image by a charging step, an exposure step, a developing step, a transfer step, and a fixing step. At the charging step, the surface of a photoreceptor is uniformly charged by a charging section. At the exposure step, a laser beam is irradiated by the exposure section to the charged photoreceptor surface and an electrostatic latent image is formed. At the developing step, the electrostatic latent image on the photoreceptor is developed by a developing section and a toner image is formed on the photoreceptor. At the transfer step, the toner image on the photoreceptor is transferred onto a recording medium by a transfer section. At the fixing step, the toner image transferred onto the recording medium is heated by a fixing section and the toner image is fixed on the recording medium.
To realize energy saving of the image forming apparatus at the above fixing step, development of a low temperature fixation toner in which a binder resin whose softening point is low is used and which is fixable at a relatively low temperature, is in process. However, by using the binder resin whose softening point is low, preservation stability of a toner decreases and a toner aggregation may be generated.
Therefore, in order to enhance the preservation stability of the toner, a surface modification treatment for coating the surfaces of toner core particles with a coating material has been performed. By coating the toner core particles and manufacturing a toner, the toner aggregation is able to be suppressed.
Japanese Examined Patent Publication JP-B2 5-10971 (1993) discloses as a method of the surface modification treatment, a method that a mechanical stirring force is applied to powder particles by a rotary stirring section such as a screw, a blade, or a rotor to fluidize the powder particles in a powder flowing passage, a liquid is sprayed from a spray nozzle to the powder particles in a fluid state, and the surfaces of the powder particles are coated by a coating material contained in the spray liquid. According to the method described in JP-B2 5-10971, adhesiveness between the coating material and the powder particles is able to be improved and time required for the surface modification treatment is able to be shortened.
Further, Japanese Unexamined Patent Publication JP-A 4-211269 (1992) discloses a method of manufacturing a microcapsule in which resin particles are adhered to the surfaces of inner core particles and the resin particles are dissolved with a solvent to form a coating layer on the surface of the inner core particle. According to the method described in JP-A 4-211269, after forming the coating layer on the surface of the inner core particle with the treatment using the solvent, a microcapsule is obtained by drying and removing.
However, with the method disclosed in JP-B2 5-10971, the coating material in the spray liquid is in a state of aggregation, and the aggregation is adhered to the surfaces of the powder particles without disintegration. Thereby, there is a problem that the film thickness of a coating material film to be formed on the surface of the powder particle is non-uniform.
Additionally, the state of aggregation of the coating material varies depending on the steps of manufacturing the coating material. The size of the disintegrated coating material varies depending on the size of the coating material in the state of aggregation. Then, depending on the size of the disintegrated coating material, a stirring period required for sufficiently adhering the coating material to the surfaces of the power particles varies. Therefore, in the method described in JP-B2 5-10971, even though the coating material is disintegrated before being adhered to the surfaces of the power particles, when the stirring period is too short, the coating material does not adhere to the surfaces of the powder particles sufficiently and the film thickness of the coating material film is still non-uniform.
On the other hand, when the stirring period is too long, the powder particles are melted with the heat generated by the stirring. There is a problem that when the powder particles contain wax or the like, by the melting of the powder particles, a release agent or the like exudes into the coating material film, and the characteristics of toner such as the fluidity and the preservation stability are degradated.
Further according to the method described in JP-A 4-211269, the solvent becomes hard to vaporize by dissolving the resin particles. Thereby, the aggregate of the inner core particles are generated or the inner core particles adhere to an inner wall surface of the manufacturing apparatus. As a result, the yield of the microcapsule is lowered. Moreover, some type of solvent may even dissolve the inner core particles. When the inner core particles are dissolved, an additive such as a release agent existed inside the inner core particles is fixed or exposed on the surfaces of the inner core particles, and the preservation stability or the like of the microcapsule is lowered.